A centrifugal fan is a mechanical device for moving air or other gases. Centrifugal fans increase the speed of an air stream with their rotating impellers. A centrifugal fan may be a drum-shaped device having a number of fan blades that are mounted around a fan wheel. The fan wheel may turn on a driveshaft which is mounted on bearings in a fan housing. A gas or air may enter from the side of the fan wheel, and the wheel may turn about 90 degrees and accelerate due to centrifugal and Coriolis forces as the gas or air flows over the fan blades and exits the fan housing.
Disclosed methods and devices herein are directed to an apparatus for use with fan systems. Typically, fan blades on the hub may be arranged in three different ways: forward-curved, backward-curved or radial Tip. Forward-curved (herein after “FC”) blades curve in the direction of the fan wheel's rotation. FC blades provide a low noise level and relatively high air flow with a high increase in static pressure. In these types of fans, flow acceleration in the blade channels may be one of the determining factors in fan performance.
Generally, the performance of FC fans may be a function of parameters that include the angle of attack at the leading edge of a blade and/or the magnitude of the separation that occurs at the suction side of a blade which may further cause a pressure loss in the fan, as well as other factors. In some cases, decreasing the angle of the blade's leading edge may decrease the entry shock loss and separation loss on the suction side of the blade. However, due to flow deceleration in the blade channel, the performance of the FC centrifugal fan may decrease. Therefore, there is a need in the art for centrifugal fan impellers in which shock loss and separation loss is decreased while maintaining the performance and efficiency of the impeller.